Common antidepressants may up dementia risk

A class of drugs commonly prescribed as antidepressants may increase the risk of dementia, even when taken 20 years before diagnosis of cognitive impairment, a study has found.

Researchers analysed over 27 million prescriptions as recorded in the medical records of 40,770 patients over age 65 diagnosed with dementia compared to the records of 283,933 older adults without dementia.

They found greater incidence of dementia among patients prescribed anticholinergic antidepressants, anticholinergic bladder medications and anticholinergic Parkinson's disease medications than among older adults who were not prescribed these drugs.

"Anticholinergics, medications that block acetylcholine, a nervous system neurotransmitter, have previously been implicated as a potential cause of cognitive impairment," said Noll Campbell, from Indiana University in the US.

"This study is large enough to evaluate the long-term effect and determine that harm may be experienced years before a diagnosis of dementia is made," said Campbell, who is also an assistant professor at Purdue University.

"These findings make it clear that clinicians need to carefully consider the anticholinergic burden of their patients and weigh other options," said Malaz Boustani, research investigator at Regenstrief Institute in the US.

"Physicians should review all the anticholinergic medications - including over-the-counter drugs - that patients of all ages are taking and determine safe ways to take individuals off anticholinergic medications in the interest of preserving brain health," Boustani said.

The study, published in the journal BMJ, utilised data from the Clinical Practice Research Datalink which includes anonymised diagnosis, referral and prescription records for more than 11 million patients from 674 primary care practices across the UK.

"This research is really important because there are an estimated 350 million people affected globally by depression. Bladder conditions requiring treatment are estimated to affect over 13 per cent of men and 30 per cent of women in the UK and US," said George Savva, visiting researcher at University of East Anglia (UEA).

"We don't know exactly how anticholinergics might cause dementia," said study co-author Chris Fox, professor at UEA.

"Further research is needed to understand possible reasons for this link. In the meantime, I strongly advise patients with any concerns to continue taking their medicines until they have consulted their doctor or pharmacist," said Fox.

"With many medicines having some anticholinergic activity, one key focus should be de-prescribing. Clinical staff, patients and carers need to work together collaboratively to limit the potential harm associated with anticholinergics," said Ian Maidment, senior lecturer at Aston University in the UK.